1. Field of the Invention
The present invention relates to radio transmitter/receivers and in particular it relates to a method of re-programming radio transmitter/receivers over-the-air (OTA).
2. Description of the Prior Art
A radio transmitter/receiver (transceiver) such as a radiotelephone is designed for operation with particular types of networks such as GSM (global system for mobile communication) 900 or DCS (digital communication system) 1800. In GSM 900 and DCS 1800, radio waves of a 900 megahertz band and an 1.8 gigahertz band are used respectively. Each of GSM 900 and DCS 1800 is a mobile communication system widely used in, for example, Europe.
Intended use of the radiotelephone with a particular network(s) in a restricted geographical area, however, requires that the telephone be configured so as properly to communicate with the particular network(s). The user of a radiotelephone will usually have a telephone which has been configured for communication with a so called “home network”. The home network is the local network usually most used by the subscriber.
The area within which a user of e.g. a GSM radiotelephone may operate, however, is considerable and is not limited to the home network but may be extended on many other networks throughout the world. Use of a handset outside the home network is known as “roaming”.
When the radiotelephone is to be used in roaming it is often necessary for it to have a configuration different to that for use with the home network. It is possible for re-configuration of radio transmitter/receivers to be effected by means of signals received across the air interface.
It is also convenient for the radio to be re-configurable over the air interface so as to support different types of communication and user applications e.g. addition of address book manager, whether or not it is located in the home network.
Over-the-air re-programming of radio receivers is well known in the art and reference may be made to U.S. Pat. No. 5,381,138 for example. The capability to obtain programming data from a network is particularly useful for a roaming radio transmitter/receiver.
When beginning operation in an area for which the radiotelephone is not configured and it is required to download the data for reconfiguration from one of the available networks, a communication link must first be established with the network of interest. It has been proposed that a pilot channel be established in all areas from which the roaming radiotelephone may obtain the data necessary for reconfiguration.
A pilot channel of this type, however, will require a relatively large bandwidth to allow a sufficiently fast transfer of the data required. Since the pilot channel is provided separately from a traffic channel used for transferring voice data and a control channel for performing control operations inherent to the particular network, establishment of the pilot channel of a relatively large bandwidth lowers utility efficiency of the frequency resources in the whole network. Further, the task of standardization of the pilot channel of a relative large bandwidth for transferring a large amount of data is considered to be complicated.